Design: This cross-sectional study included 711 participants from the African-PREDICT study (African Prospective study on the Early Detection and Identification of Cardiovascular Disease and Hypertension), which is an ongoing study held at the North-West University, Potchefstroom, South Africa (Strauss et al, 2017); the cohort included black 51%, women 58%, 24.83.02 years. Methods: We assessed cardiac geometry and function by two-dimensional echocardiography and pulse wave Doppler imaging. 24-Hour urinary marinobufagenin (MBG) and sodium excretion were measured, and the estimated glomerular filtration rate determined. Results: Across MBG excretion quartiles, left ventricular mass ( P<0.001), end diastolic volume (P<0.001), stroke volume ( P=0.004) and sodium excretion ( P<0.001) were higher within the fourth compared with the first quartile. Partial regression analyses indicated that left ventricular mass (r=0.08, P=0.043), end diastolic volume ( r=0.10, P=0.010) and stroke volume ( r=0.09, P=0.022) were positively related to MBG excretion. In multivariate-adjusted regression analysis, left ventricular mass associated positively with MBG excretion only in the highest MBG excretion quartile (adjusted R2=0.20; =0.15; P=0.043). This relationship between left ventricular mass and MBG excretion was evident in women (adjusted R2=0.06; =0.127; P=0.015) but not in men (adjusted R2=0.06; =0.007; P=0.92). Conclusions: Left ventricular mass positively and independently associates with MBG excretion in young healthy adults with excessively high marinobufagenin excretion. Women may be more sensitive to the effects of MBG on early structural cardiac changes.